Meet Mike in Leesburg Next Month
Mike will appear at 11 a.m. and 1:30 p.m. on Sunday, April 19 at the Leesburg Flower & Garden Festival.
It’s almost time to apply corn gluten meal for crabgrass prevention and legal lawn feeding
Susan, “just outside of D.C.,” writes: “I’m using corn meal gluten for the first time this year to try and avoid some weeds. But it keeps raining. Does the ground have to be dry to apply it, especially since the directions say to water it in any way?”
Timing Tip No. 1: Dry, then wet, then dry
Back in the 90s, Iowa State researchers discovered that corn gluten meal — a byproduct of corn starch manufacture — was both a perfect natural lawn fertilizer and pre-emergent herbicide that could feed your lawn and help prevent the germination of dormant weed seeds, like crabgrass.
To get the most weed prevention power, corn gluten meal should ideally be applied to somewhat dry soil, watered in and then allowed to dry out. Now in the world of pesky physical reality, spring soils are always somewhat damp, so I would aim my application more towards an upcoming dry spell (no rain) after application.
It’s easy for most people to add water to their lawn following an application, but really hard, as John Fogerty famously noted, to “stop the rain.”
Timing Tip No. 2: Soil temp
As we’ve said, corn gluten meal is both a perfect natural lawn fertilizer and pre-emergent herbicide that can help prevent weeds like crabgrass. But, as with chemical pre-emergents, the timing is critical. Apply it after the weed seeds have already sprouted and no type of pre-emergent will have any effect.
Crabgrass seed germinates at a soil temperature of 55 degrees, as measured four inches down. Ideally, you want to apply the material about a week before that — just as soil temperatures reach around 50 degrees four inches deep. We are not there yet.
In 2013, the first week of April was the ideal time. Last spring, the harsh winter pushed it back to around April 5. So while this is the ideal time to get your gluten in hand, you should wait at least another week to apply it.
How to tell your soil temp
You can, of course, buy your own soil thermometer, which would instantly mark you as a person of great gardening wisdom (and/or super-geekdom). Make sure the probe is inserted four inches deep. That’s the level that experts always refer to for seed germination and planting temps. There are also two great sources you can turn to for local soil temp info.
- The U.S. Department of Agriculture’s soil probe at Powder Mill in Prince George’s County, Maryland. Find the most recent date (at the bottom), and then go over to the column that says “STO.I-1:-4 (degC).” But it’s in Celsius. Go here to convert it to Fahrenheit. (Or do the math: multiply the Celsius number by 1.8 and then add 32.) On Thursday, the probe indicated that we were just under 42 degrees F, a number that applies to the soils in most of our region. (It’s a good location for extrapolation.) But in the heat sink of the city, where the soil will be a bit warmer, I would act when that number hits around 46 to 48 instead of 50.
- The other site monitors the water temperature at several locations in the bay, and as an alert listener pointed out to me years ago, those numbers almost exactly mimic the temperature of the soil at the closest location on land. (And these numbers are in Fahrenheit—just scroll down past the map to the listings.)
A final word about corn gluten meal….
Since the new lawn care regulations in Maryland and Virginia limit the amount of Nitrogen you’re allowed to apply to your lawn to pretty much the exact amount found in natural fertilizers like corn gluten meal, you might as well do the right thing and choose corn gluten — an all-natural slow-release fertilizer — over old-school chemical salts. It’s like giving the bay a nice tip for its good service.
A word or six about crabgrass in general
Last year’s mild summer should have led to a minimum of crabgrass, so if your lawn still had a lot of it, you really need to change your lawn care habits as crabgrass should only be an issue in summers with multiple prolonged heat waves — of which there were zero last year. Ahem.
So yes, be ready to spread crabgrass-preventing corn gluten meal on your lawn around the first week of April. But also:
- Get a new blade for your mower or have the old one sharpened. A dull blade breeds weeds.
- Adjust the cutting height so that three inches of lawn remains after cutting. Scalping guarantees weeds.
- Never cut the lawn when its wet. Because I said so.
- And throw away any bagging attachments. Those pulverized clippings provide a gentle supplemental feeding for your turf every time you mow.
And that’s it—no chemicals or magic organics! The best way to prevent lawn weeds is with a sharp, three-inch cut and returning your clippings to the turf.
Getting better holly berries
Beth in Silver Spring writes: “I planted three female winterberry hollies and one compatible male variety two years ago in the fall. They’re fairly tall and gangly, with minimal berry production. Someone at the nursery told me that pruning in March could help them bush out more and produce larger fruit. Is that a good idea?”
No, Beth; it is not.
First, congratulations on planting a male pollinator for your girls. Lack of a male is the biggest cause of barren bushes.
Second, be patient! Your hollies are still very young and need a few years to mature. And your plants will be flowering soon. Flowers = berries. Pruning now removes potential flowers. So leave them alone until the berries begin to visibly form, and then you can prune off unproductive branches. But don’t wait too long—you want to prune when the berries are still small to avoid summer heat stress on the plants.
Oh and note that hollies will never do well if they are mulched with wood (but they would love a mulch of an inch of peat moss covered with an inch of compost instead), fed chemical fertilizers (which can impede flowering), or if they don’t get a good amount of sun.
The fact that you say yours are tall and leggy makes me wonder about how much sun they get…
